Types of Operating Systems for Computer Science.pptx
- 1. CSC351-Operating System Week-1 Lecture-2 Semester 05 Prepared by: Dr. M. Abubakar Qazi
- 2. Agenda for today ► Single-user systems ► Batch systems ► Multiprogram systems ► Time-sharing systems ► Distributed systems ► Real-time systems ► Mobile OS ► Interrupts, traps, and signals ► CPU, I/O, and memory protection Interactive Lahore Garrison University 2
- 3. Single user systems ► Personal computers – computer system dedicated to a single user.(many but 1 at a time) ► Interactive(Accepting input from a human. Interactive computer systems are programs that allow users to enter data or commands. Most popular programs, such as word processors and spreadsheet applications, are interactive. ► A non interactive program is one that, when started, continues without requiring human contact. A compiler is a non interactive program) ► User convenience and responsiveness. Lahore Garrison University 3
- 4. Batch systems ► First Fundamental system. ► User operator ► Reduce setup time by batching similar jobs ► Automatic job sequencing – automatically transfers control from one job to another. ► Resident monitor : ► initial control in monitor ► control transfers to job ► when job completes ► control transfers back to monitor Lahore Garrison University 4
- 5. Memory layout of batch systems Lahore Garrison University 5
- 6. Batch system (conti…) Lahore Garrison University 6
- 7. Multiprogrammed systems Sharing the processor, when two or more programs reside in memory at the same time, is referred as multiprogramming Multiprogramming increases CPU utilization by organizing jobs so that the CPU always has one to execute. Several jobs are kept in main memory at the same time, and the CPU is multiplexed among them. Multiprogramming operating systems monitor the state of all active programs and system resources using memory management programs to ensures that the CPU is never idle, unless there are no jobs to process. Lahore Garrison University 7
- 8. Multiprogrammed Systems Example: Two processes P1 and P2 with CPU and I/O bursts of one time unit each Lahore Garrison University 8 P1 P2 … CPU Burst I/O Burst P1 P2
- 9. Os features needed for Multiprogramming ► Spooling (Simultaneous Peripheral Operation On-Line)(put job in buffer) ► Memory management ► CPU scheduling Lahore Garrison University 9
- 10. Time sharing systems ► A multi user and multi process system. ► An interactive system with multiprogramming ► To obtain a reasonable response time, jobs may have to be swapped in and out of main memory. ► UNIX, Linux, Widows NT server, and Windows 2000 server Lahore Garrison University 10
- 11. Distributed Operating System Distributed systems use many central processors to serve multiple real-time applications and users. As a result, data processing jobs are distributed between the processors. It connects multiple computers via a single communication channel. Furthermore, each of these systems has its own processor and memory. Additionally, these CPUs communicate via high-speed buses or telephone lines. Individual systems that communicate via a single channel are regarded as a single entity. They're also known as loosely coupled systems.
- 12. Real Time systems ► A data processing system in which the time interval required to process and respond to inputs is so small that it controls the environment ► the time taken by the system to respond to an input and display of required updated information is termed as the response time ► A real-time operating system must have well-defined, fixed time constraints, otherwise the system will fail such as controlling scientific experiments, medical imaging systems, industrial control systems, and some display systems. Plane landing. Ventilators. ► Real-Time systems may be either hard or soft real-time. Lahore Garrison University 12
- 13. Real Time systems Hard real-time systems: ► Secondary storage limited are absent, data stored in short term memory, or read-only memory (ROM).coz time is short ► No virtual memory—time cannot be “wasted” on translation of logical to physical addresses. ► OS code structured for efficiency ► Plane landing systems, process control in nuclear power plants, ventilators, etc. Lahore Garrison University 13
- 14. Real time systems (Cont..) Soft real-time systems ► Output should be produced within the given time constraints but if it is not, the result is not life threatening. ► Useful in applications (Live Video Streaming) requiring advanced operating-system features Mobile Communication Music Playing Robots Weather Station Lahore Garrison University 14
- 15. Mobile OS OS for smartphones, tablets, and PDA’s. It is a platform on which other applications can run on mobile devices. Examples of the Mobile OS: Android OS, ios, Symbian OS, and windows mobile OS
- 16. Interrupts Interrupts are signals sent to the CPU by external devices, normally I/O devices. They tell the CPU to stop its current activities and execute the appropriate part of the operating system After the interrupt signal is sensed, the computer either resumes running the current program or begins running another program. An operating system usually has some code that is called an interrupt handler. The interrupt handler prioritizes the interrupts and saves them in a queue if more than one is waiting to be handled.
- 17. Interrupts, Traps and Signals Interrupt---an event generated by a device in a computer to get attention of the CPU(from hardware devices) Trap—an event by the CPU itself as it executes a program Signal—an event generated by a user Lahore Garrison University 17
- 18. Interrupts, trap, signals If you press any key(keyboard) or moving the mouse…..Example of interrupt Hardware may trigger an interrupt at any time by sending a signal to the CPU usually by way of the system bus. Software may trigger an interrupt by executing a special operation called a system call Lahore Garrison University 18 Answer the Phone . . . Resume
- 19. Interrupts, trap, signals ► A process can generate a trap, for example, by dividing a number by zero. ► caused either by an error (division by zero or invalid memory access) or by a user request for an operating system service. ► A user or a process may generate a signal (an interrupt to a process) Lahore Garrison University 19
- 20. Interrupt handling ► In case of interrupt or trap, the CPU invokes a piece of code in the OS to service it, known as interrupt service routine(ISR) or trap service routine(TSR) ► In case of signal, the process can take one of the three possible actions , default action as defined by OS, ignore signal, or take a programmer specified action Lahore Garrison University 20
- 21. Interrupt handling (Cont..) ► Interrupt transfers control to the interrupt service routine, generally, through the interrupt vector, which contains addresses of all the interrupt service routines. ► Interrupt architecture must save the address of the instruction after the interrupted instruction and the CPU state so that execution of the interrupted process may continue after the interrupt has been serviced. Lahore Garrison University 21
- 22. As we have time sharing system so multiple user may be there. Here comes the issue of protection One user may delete the files of others. Or may overwrite program in memory
- 23. Hardware protection ► Dual-Mode Operation ► I/O Protection ► Memory Protection ► CPU Protection Lahore Garrison University 23
- 24. Dual Mode Operation ► Sharing system resources requires operating system to ensure that an incorrect program cannot cause other programs to execute incorrectly. ► Provide hardware support to differentiate between at least two modes of operations. ► User mode – execution done on behalf of a user. ► Monitor mode (also kernel mode or system mode) – execution done on behalf of operating system. Lahore Garrison University 24
- 25. Dual Mode Operation ► Mode bit added to computer hardware to indicate the current mode: monitor (0) or user (1). ► When an interrupt or fault occurs hardware switches to monitor mode. ► Privileged instructions can be issued only in monitor mode. Lahore Garrison University 25 monitor user Interrupt/fault set user mode
- 26. Reference To cover this topics , different reference material has been used for consultation. Operating systems concept by Abraham siberchatz edition 9 Tutorialspoint.com Google.com 26 Lahore Garrison University
Editor's Notes
- #4: Examples of Batch OS: payroll system, bank statements, data entry, etc.